The new office building at 1200 Intrepid Ave., in the Philadelphia Navy Yard Corporate Center is a sight to behold, described by some as gravity defying in that parts of the structure are designed to replicate the shape of a ship's hull, narrow at the bottom and wide at the top.
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Location: Maryland Heights, Mo.
Type of Precast: CarbonCast® Architectural Cladding
Square footage: 198,100 sq. ft. (approx. 40,000 sq. ft. precast)
CarbonCast Replicates Look (But Not Cost) of Limestone
When Edward Jones set out on a multi-phase expansion of its suburban St Louis North Campus, architect Arcturis recommended the classic yet contemporary look of limestone. The first project, an office building dubbed “B2,” was to showcase nearly 50,000 sq. ft. of the expensive imported material on its exterior.
Sleek and urbane, the B2 building at 170 Edward Jones Boulevard is a six-story, 198,100 sq. ft. steel structure featuring sun-shading devices, interior light shelves, raised access flooring and direct/indirect lighting. Built to house approximately 800 occupants, B2 shares a four-acre site with a 312,500 sq. ft. campus parking garage with capacity for 958 cars. Arcturis provided planning, architecture, interiors and facilities services for the project.
The extensive use of limestone created budget problems for the project. Early on, Arcturis sought alternative materials that would meet the performance and aesthetic requirements it had agreed with Edward Jones. In the process, they consulted with High Concrete Group LLC for a precast concrete solution that would capture the same look.
To maintain the schedule and control costs, the design team needed a skin with a design weight of 50 lbs per sq. ft. or less. They found their solution in CarbonCast, a lightweight precast concrete using C-GRID® carbon fiber reinforcement technology that offers remarkable aesthetic versatility.
CarbonCast replaces conventional welded wire mesh reinforcement in the face of precast cladding panels with C-GRID carbon fiber grid. Used to control concrete cracking, C-GRID will not corrode which allows precasters to use significantly less concrete cover, saving weight and concrete. Further weight savings are achieved by substituting panel mass with foam. CarbonCast panels are up to 50% or more lighter in weight than conventional precast concrete panels yet yield the same performance and appearance qualities.
For the B2 project, High engineered 8-inch thick CarbonCast Architectural Panels consisting of a two-inch face backed with six inches of EPS foam insulation. Steel-reinforced ribs on 4’ centers provided structural strength.
The design cut the weight of the precast panels to 50 pounds per square foot, compared to 100+ pounds per square foot for conventional precast. The weight reductions eliminated the need for a costly and time consuming structural redesign.
“Without CarbonCast, we would have looked at a metal panel,” says Steve Hoover. LEED AP, project architect at Arcturis. “But after we chose limestone, we knew metal would not give us the aesthetic we wanted. With precast we knew we were going to get a product that would closely replicate the original design intent.”
Use of the limestone was limited to the first floor, treating visitors to subtle veining and a buff color in a brush-hammered finish. Above, the precast architectural panels are formed into a 30” x 60” stack bond appearance on floors two through six using identical-width reveals and panel joints. Finished with a light sandblast, the buff-color panels create the illusion of monolithic limestone blocks.
“CarbonCast helped us make the strong design statement we wanted,”
Hoover says. In fact, the Edward Jones project won Best Office Structure in the PCI Design Awards competition.
The precast elements were fabricated off-site and delivered for immediate erection, eliminating the material and equipment storage concerns of field-construction methods. Because precast concrete is manufactured in a controlled factory environment, weather delays and other setbacks were virtually eliminated, expediting enclosure of the building and allowing other subcontractors ample time for their responsibilities.
In addition, the CarbonCast cladding panels provide insulation values typically not available in conventional precast or other competitive systems. The addition of EPS insulation enables R-value contribution. Savings on energy to heat and cool the building are anticipated.
CarbonCast is a registered trademark of AltusGroup, Inc.
C-GRID is a registered trademark of Chomarat N.A.